1. Technical Field of the Invention
This invention relates generally to radio technology and more particularly to a radio receiver.
2. Description of Related Art
As is known, handheld digital audio systems are becoming very popular. Such systems include digital audio players/recorders that record and subsequently playback MP3 files, WMA files, etc. Such digital audio players/recorders may also be used as digital dictaphones and file transfer devices. Further expansion of digital audio players/recorders includes providing a frequency modulation (FM) radio receiver such that the device offers FM radio reception.
With most radio receivers, and particularly with FM Radio Receivers, minimizing noise is desirable. A typical FM receiver receives a wideband signal (e.g., 76 MHz to 108 MHz) that includes a plurality of channels (e.g., FM radio channels are spaced at 100 KHz). A low noise amplifier amplifies the received wideband FM signal, which is subsequently mixed with a local oscillation to produce an intermediate frequency (IF) signal. The intermediate frequency signal is mixed with a second local oscillation to produce a baseband signal. In each of these steps, if noise or distortion is above a desired level, the resulting baseband signal will have reduced fidelity. Further, in silicon CMOS implementations of a radio receiver, noise and distortion problems can be more severe than in traditional RF IC process technologies. CMOS transistors have less favorable noise and distortion performance compared to bipolar transistors. Therefore, RF IC designs implemented in silicon CMOS processes have different requirements and tradeoffs concerning noise and distortion. Additional complications arise in silicon CMOS RF design, in that digital circuitry is sometimes included in the same IC. The digital circuitry on the IC generates much more substrate noise and clock spurious responses, than traditional RF implementations. Managing the RF design in the presence of digital circuitry requires new mixed signal architectures and techniques in a silicon CMOS process.
Therefore, a need exists for a method and apparatus for a low noise low distortion radio receiver front end for use in a mixed signal environment.